One question still hanging over the Manafort case is whether President Trump might grant him a pardon. This would not affect those state charges that Ryan just mentioned, but it could apply to his federal convictions. After the sentencing today, a reporter asked President Trump about the possibility of pardon for Manafort.

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PRESIDENT DONALD TRUMP: I have not even given it a thought as of this moment. It's not something that's right now in my mind. I do feel badly for Paul Manafort. That I can tell you.

CORNISH: To talk about how other presidents have used this power, we called Mark Osler. He's a law professor at the University of St. Thomas in Minnesota where he specializes in issues of sentencing and clemency. He says a politically controversial pardon does have historical precedent.

MARK OSLER: Probably the one that fits this the best would be the group that George H.W. Bush gave clemency to in the wake of the Iran-Contra scandal that included Caspar Weinberger. And there you had people that, as with Paul Manafort, were tied to the president in some way and had been involved in scandal with international implications.

CORNISH: There was also the case of President Clinton pardoning Marc Rich. Tell us what happened there.

OSLER: Yeah. Marc Rich is something that was very controversial at the time and still is with many people. He was convicted of offenses related to arms dealing, but he went on the lam and hid out in Switzerland. And while he was on the lam, in the last days of his presidency, President Bill Clinton gave him a pardon. And it was controversial in large part because his ex-wife had given a large donation to the Clinton Library.

CORNISH: Controversial pardons are not without consequences, right? I mean, if you think back to 1974 in the wake of Watergate, Richard Nixon got a pardon from President Gerald Ford, and there was fallout for that, right?

OSLER: Absolutely. And it may have cost him the election to Jimmy Carter. We don't often see that kind of controversial use of clemency until the end of a term. But this president may be different. You have to remember that he's already, for example, given clemency to Joe Arpaio, and that was very controversial, and he did that close to the start of his term.

CORNISH: You know, if there can be such huge political consequences for a president, why issue pardons in this way?

OSLER: Presidents do it for a variety of reasons. Sometimes it is in the interests of national reconciliation. We see that going back to the very first one - people involved in the Whiskey Rebellion, an uprising by farmers in the western part of Pennsylvania. There was a killing of a federal official, and the militia was called up by George Washington. And he gave clemency to the whiskey rebels he led the militia against. But sometimes it's because of personal allegiance. Bill Clinton giving clemency to his brother Roger is one example. And Paul Manafort would definitely fit into that category. It's hard to see how this one would be in the national interest.

CORNISH: This is a power that of course has the potential to be abused. Have there been conversations? Is there an argument for dialing it back somehow, curbing the executive branch's powers here?

OSLER: There have been, and Congress has talked about bills, and at least one has actually been introduced that would somehow effect the president's power to issue clemency. I think we have to proceed very cautiously there because we worry about a few of these aberrant cases where people who didn't deserve them get clemency. But what it would limit would be everything else that clemency does.

President Obama recently granted clemency to nearly 2,000 people. Almost all of them were people that were over-sentenced for crack, were doing life sentences that were grossly disproportionate to what their crime was. And so if we restrict this ability based on a few aberrational cases, we risk also throwing out those cases for which the framers put it into the Constitution. And that would be really a tragedy.

CORNISH: Mark Osler - he's a law professor at the University of St. Thomas in Minnesota. Thank you for speaking with us.